Wiper device with elastic bush for absorbing excess load

ABSTRACT

A wiper device for a vehicle which, when abnormal load is applied, absorbs the abnormal load so that wiping operation by a wiper blade can be carried out continuously. The wiper device is compact, and dimensional management thereof is easy. One end of a first crank lever forming a portion of a crank arm is attached to an output shaft, whereas a cylindrical portion is fixed by caulking to another end of the first crank lever by a pin. An annular portion is formed at one end of a second crank lever. An elastic rubber bush is interposed between the cylindrical portion and the annular portion. The first crank lever and the second crank lever are supported by the elastic rubber bush so as to be freely rotatable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wiper device for a vehicle whichabsorbs an abnormal load applied thereto.

2. Description of the Prior Art

Conventionally, in wiper devices for vehicles, there is a drawback inthat when the wiper device is operated with, for example, snow havingaccumulated on the wiper wiping range, the wiper blades collide againstthe accumulated snow such that the wiping operation is hampered.Therefore, abnormal load is generated at the wiper blades, and theoperation of the entire wiper device stops.

In order to overcome this drawback, Japanese Utility Model No. 5-56694discloses a wiper device for a vehicle which absorbs abnormal load suchthat continuous operation is possible.

As illustrated in FIGS. 10 and 11, in this wiper device, a first linkrod 113 and a first pivot lever 114 are connected via a segment lever115. The segment lever 115 is formed by a first connecting portion 121,which is supported so as to rotate freely with the first pivot lever114, and a second connecting portion 122, which is set apart from thefirst connecting portion 121. The second connecting portion 122 is fixedby a second connecting pin 114c at whose outer periphery a buffer member110 is disposed. In accordance with this wiper device, when abnormalload is applied, the segment lever 115 rotates around the firstconnecting portion 121 a predetermined angle with respect to the firstpivot lever 114. The buffer member 110 compressively deforms in theradial direction in accordance with the rotation of the segment lever115, so that the abnormal load can be absorbed.

However, in this disclosed art, the first pivot lever 114 and thesegment lever 115 are attached at the first connecting portion 121 so asto be freely rotatable. A drawback arises in that, because there isjoggling between the first connecting portion 121 and the segment lever115, the dimensions of the first connecting portion 121 and the segmentlever 115 must be strictly managed during manufacturing.

The rotational angle of the segment lever 115 is determined by the outerdiameter dimension of the buffer member 110. Therefore, a drawbackarises in that, in order to handle abnormal loads of wiper deviceshaving large wiping angles, the outer diameter of the buffer member 110must be made large, which leads to an increase in the size of the wiperdevice.

Other art related to the present invention are disclosed in U.S. Pat.No. 4,765,018; DE 3734309A1; DE 2820104A1; and FR 2557051.

SUMMARY OF THE INVENTION

In view of the aforementioned, an object of the present invention is toprovide a wiper device for a vehicle which absorbs abnormal load so thatwiping operation can be carried out continuously, and which is compact,and in which dimensional management is easy.

An aspect of the present invention is a wiper device for a vehiclecomprising: a crank arm connected to an output shaft of a motor; a linkrod connected to the crank arm so as to be freely rotatable; a pivotlever connected to the link rod so as to be freely rotatable; and awiper arm connected to the pivot lever via a pivot shaft, wherein thecrank arm is formed by a first lever which is connected to the outputshaft, a second lever which is connected to the link rod so as to befreely rotatable, and an elastic bush which torsionally deformselastically in accordance with relative rotation between the first leverand the second lever.

In accordance with the present invention, during normal wiper operation,the first lever and the second lever are interlocked with the motor anddo not rotate relatively. On the other hand, when abnormal load isgenerated (e.g., when the wiping range is narrowed due to accumulatedsnow), the abnormal load is transmitted to the crank arm via the wiperarm and the pivot shaft. As a result, the abnormal load is applied tothe crank arm. At this time, the elastic bush torsionally deformselastically in accordance with the relative rotation between the firstlever and the second lever, and absorbs the abnormal load. Further,because the first lever and the second lever rotate relatively, even ifthe wiper arm is forcibly stopped, the motor can be operatedcontinuously.

The first lever and the second lever are connected via the elastic bushwhich torsionally deforms elastically. Therefore, there is no jogglingbetween the first lever and the second lever. As a result, management ofthe dimensions of the first lever and the second lever and management ofthe dimension between the first lever and the second lever arefacilitated.

During normal operation of the wiper, the elastic bush absorbs thevibration transmitted from the wiper arm. Therefore, the vibration ofthe first lever can be made extremely small.

Further, the range over which the first lever and the second lever canrotate relatively can be varied merely by varying the torsional rigidity(torsional characteristic) of the elastic bush. Therefore, there is noneed to make the outer radius of the elastic bush large with respect tothe abnormal load of a wiper device for a vehicle having a large wipingangle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating the basic structure of a first embodimentand a second embodiment of a wiper device for a vehicle relating to thepresent invention.

FIG. 2 is a cross-sectional view taken along line 2--2 of FIG. 1 andillustrating a crank arm.

FIG. 3 is a view for explaining operation of the wiper device for avehicle of the first embodiment.

FIG. 4 is a cross-sectional view corresponding to FIG. 2 andillustrating a variant example of the crank arm.

FIG. 5 is a cross-sectional view corresponding to FIG. 2 andillustrating another variant example of the crank arm.

FIG. 6 is a cross-sectional view taken along line 6--6 of FIG. 7 andillustrating a pivot lever of the wiper device for a vehicle of thesecond embodiment of the present invention.

FIG. 7 is a view for explaining operation of the wiper device for avehicle of the second embodiment.

FIG. 8 is a cross-sectional view corresponding to FIG. 6 andillustrating a variant example of the pivot lever.

FIG. 9 is a cross-sectional view corresponding to FIG. 6 andillustrating another variant example of the pivot lever.

FIG. 10 is an explanatory view illustrating the basic structure of aconventional wiper device for a vehicle.

FIG. 11 is a view illustrating in detail a first pivot lever and a firstconnecting portion of the conventional wiper device for a vehicle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments actualizing the wiper device for a vehicle of the presentinvention will be described hereinafter on the basis of FIGS. 1 through9.

First Embodiment!

As illustrated in FIG. 1, at a wiper device 1 for a vehicle, one end ofa crank arm 12 is attached to an output shaft 11 of a wiper motor 3. Aball pin 12f is attached to the other end of the crank arm 12. One endof a link rod 13 is connected to the ball pin 12f so as to be freelyrotatable. The other end of the link rod 13 is connected to one end of apivot lever 14 so as to be freely rotatable. A pivot shaft 15, to whichone end of a wiper arm 16a is attached, is fixed to the other end of thefirst pivot lever 14. One end of a link rod 18 is connected to thesubstantial center of the pivot lever 14 so as to be freely rotatable.One end of a second pivot lever 19 is connected to the other end of thelink rod 18 so as to be freely rotatable. A pivot shaft 17, to which oneend of a wiper arm 16a' is attached, is fixed to the other end of thepivot lever 19. The respective other ends of the wiper arms 16a, 16a'are rotatably fixed to substantially central portions of wiper blades16b, 16b'.

As illustrated in FIG. 2, the crank arm 12 which is attached to anoutput shaft 11 is basically formed by a first crank lever 12a which ismetal and serves as a first lever, a second crank lever 12b which ismetal and serves as a second lever, and an elastic rubber bush 10 whichserves as an elastic bush and will be described in detail later.

One end of the first crank lever 12a is fixed to the output shaft 11 viaa nut 11a. The other end of the first crank lever 12a is strongly fixedby caulking to a metal cylindrical portion 12c by a pin 12d.

An annular portion 12e, whose inner diameter is greater than the outerdiameter of the cylindrical portion 12c, is formed at one end of thesecond crank lever 12b. The ball pin 12f is fixed to the other end ofthe second crank lever 12b. One end of the link rod 13 is connected tothe ball pin 12f so as to be freely rotatable.

The elastic rubber bush 10 is disposed between the outer peripheralsurface of the cylindrical portion 12c and the inner peripheral surfaceof the annular portion 12e. The elastic rubber bush 10 is adhered andfixed, by vulcanization or the like, to the outer peripheral surface ofthe cylindrical portion 12c and to the inner peripheral surface of theannular portion 12e. The elastic rubber bush 10 supports the first cranklever 12a and the second crank lever 12b such that the first crank lever12a and the second crank lever 12b are freely rotatable, and connectsthe first crank lever 12a and the second crank lever 12b. The elasticrubber bush 10 of the present embodiment has high torsional rigidity(torsional characteristic). As a result, the elastic rubber bush 10 hasrestoring force for returning to its original state from its twistedstate. Examples of the material which may be used for the elastic rubberbush 10 include styrene butadiene rubber (SBR), natural rubber (NR),chloroprene rubber (CR), compounds of these rubbers, thermoplasticurethane elastomers, and the like.

In operation, the rotational power of the wiper motor 3 is transmittedto the pivot shaft 15 via the crank arm 12, the link rod 13 and thepivot lever 14, so that the wiper arm 16a and the wiper blade 16b arerotated reciprocally. Further, the rotational power of the wiper motor 3is transmitted to the pivot shaft 17 via the pivot lever 14, the linkrod 18 and the pivot lever 19, so that the wiper arm 16a' and the wiperblade 16b' are rotated reciprocally.

Accordingly, as illustrated in FIG. 3, at normal times (times when noabnormal load is applied due to accumulated snow or the like), when thewiper device 1 for a vehicle is operated, the wiper blade 16b rotates tothe lower reversal position 0 illustrated by the two-dot chain line. Thewiper arm 16 and the first pivot lever 14 at this time are at positions0' and 0", respectively, which are illustrated by the two-dot chainlines. In order to simplify explanation, the second pivot lever 19 side,at which the wiper arm 16a', the wiper blade 16b' and the like areshown, is omitted from FIG. 3.

When the wiper device 1 for an automobile is operated on anunillustrated windshield glass surface when, for example, snow hasaccumulated thereon, load is applied when the wiper blade 16b attemptsto wipe the accumulated snow (the hatched portion S in FIG. 3). Whenthis load is greater than the rotational force of the wiper blade 16b,in a state in which the wiper blade 16b abuts the accumulated snow S,abnormal load is applied to the wiper blade 16b and the wiping range ofthe wiper blade 16b is narrowed. Specifically, due to the accumulatedsnow S, the rotation of the wiper blade 16b to the normal lower reversalposition 0 is impeded, and the wiper blade 16b is forcibly stopped atthe limited lower reversal position Q.

When the wiper blade 16b is forcibly stopped at the limited lowerreversal position Q, because the elastic rubber bush 10, whichshaft-supports the first crank lever 12a and the second crank lever 12bsuch that they are relatively rotatable, is provided at the crank arm12, the elastic rubber bush 10 torsionally deforms elastically, and thesecond crank lever 12b rotates with respect to the first crank lever 12a(state B in FIG. 3). Because the second crank lever 12b rotates withrespect to the first crank lever 12a, the rotational operation of thewiper motor 3 is continuous. Specifically, the first crank lever 12a andthe second crank lever 12b change successively from state A to state B,and from state B to state C. Therefore, the rotational operation of thewiper motor 3 is continuous until the locking of the wiper blade 16bwhich is at the limited lower reversal position Q is canceled.

In accordance with the wiper device for a vehicle of the firstembodiment, the elastic rubber bush 10, which shaft-supports the firstcrank lever 12a and the second crank lever 12b such that they arerelatively rotatable, is provided at the crank arm 12. The elasticrubber bush 10 torsionally deforms elastically, and the second cranklever 12b rotates with respect to the first crank lever 12a. Therefore,the rotational operation of the wiper motor 3 can be carried outcontinuously. Accordingly, there are no drawbacks such as those of theprior art in which the wiper blade 16b is forcibly locked due to theabnormal load and the operation of the entire wiper device 1 for avehicle stops.

Further, the rotating portions of the first crank lever 12a and thesecond crank lever 12b are connected by the elastic rubber bush 10.Therefore, there is no joggling between the first crank lever 12a andthe second crank lever 12b, and management of the dimensions of thewiper device for a vehicle during manufacturing is facilitated.Accordingly, there is no need to strictly manage the dimensions duringmanufacturing in order to prevent joggling, as there is in theconventional art. As a result, manufacturing costs can be reduced.

Further, vibrations, which are generated by the wiper blade 16b duringnormal wiper wiping operation and which are transmitted to the firstcrank lever 12a via the first pivot lever 14, the link rod 13 and thesecond crank lever 12b, are absorbed by the elastic rubber bush 10.Therefore, vibration of the wiper device 1 can be reduced.

Moreover, the range over which the first crank lever 12a and the secondcrank lever 12b are relatively rotatable can be changed merely bychanging the torsional characteristic of the elastic rubber bush 10.Therefore, there is no need to make the outer diameter of the elasticrubber bush 10 large with respect to the abnormal load of the wiperblade 16b having a large wiping angle. Accordingly, the wiper device 1for a vehicle can be made compact as compared with a conventional wipingdevice for a vehicle.

In the present embodiment, the other end of the first crank lever 12a isstrongly fixed by caulking to the metal cylindrical portion 12c by thepin 12d. However, the fixing of the other end of the first crank lever12a to the cylindrical portion 12c is not limited to caulking. Forexample, as illustrated in FIG. 4, the first crank lever 12a and thecylindrical portion 12c are formed integrally by sintered metal or thelike. In this way, the number of parts can be reduced, and there is noneed to carry out fixing by caulking. Therefore, the manufacturing costsof the wiper device for a vehicle can be reduced.

Further, as illustrated in FIG. 5, at the first crank lever 12a and thesecond crank lever 12b, the positional relationship between thecylindrical portion 12c and the annular portion 12e (the relationshipbetween the inner periphery and the outer periphery) can be reversed. Inthis case, the cylindrical portion 12c and the annular portion 12e areconnected by a rivet 12d so as to be freely rotatable.

Second Embodiment!

As illustrated in FIGS. 6 and 7, the pivot lever 14 of the secondembodiment basically comprises a first pivot lever 14a which is metaland serves as a first lever, a second pivot lever 14b which is metal andserves as a second lever, and an elastic rubber bush 20 which will bedescribed in detail later. In the present embodiment, members which arethe same as those of the first embodiment are denoted by the samereference numerals, and description thereof is omitted.

As shown in FIG. 6, one end of the first pivot lever 14a is attached tothe pivot shaft 15. The other end of the first pivot lever 14a isstrongly fixed by caulking to the metal cylindrical portion 14c by thepin 14d.

The annular portion 14e, which has an inner diameter which is greaterthan the outer diameter of the cylindrical portion 14c, is formed at oneend of the second pivot lever 14b. The ball pin 14f is fixed to thesubstantial center of the second pivot lever 14b. One end of the linkrod 13 is connected to the ball pin 14f so as to be freely rotatable(see FIG. 7).

The elastic rubber bush 20 is disposed between the outer peripheralsurface of the cylindrical portion 14c and the inner peripheral surfaceof the annular portion 14e. The elastic rubber bush 20 is adhered andfixed, by vulcanization or the like, to the outer peripheral surface ofthe cylindrical portion 14c and to the inner peripheral surface of theannular portion 14e. Specifically, the elastic rubber bush 20shaft-supports the first pivot lever 14a and the second pivot lever 14bsuch that they are freely rotatable, and connects the first pivot lever14a and the second pivot lever 14b. The elastic rubber bush 20 of thepresent embodiment has high torsional rigidity. As a result, the elasticrubber bush 20 has restoring force for returning to its original statefrom its twisted state. The same materials as those used for the elasticrubber bush 10 described in the first embodiment can be used for theelastic rubber bush 20 as well.

A cylindrical projecting portion 14g is strongly fixed by caulking tothe substantial center of the first pivot lever 14a by a pin 14k. Anelongated insertion hole 14h, in which the projecting portion 14g isinserted with degrees of freedom, is provided at the other end of thesecond pivot lever 14b.

When abnormal load is applied to the wiper blade 16b in operation, theabnormal load is transferred to the wiper arm 16a, the pivot shaft 15and the first pivot lever 14a (see FIG. 7). The elastic rubber bush 20,which supports the first pivot lever 14a and the second pivot lever 14bsuch that they are relatively rotatable, is provided at the first pivotlever 14. Therefore, when abnormal load is applied, the elastic rubberbush 20 torsionally deforms elastically, and the second pivot lever 14brotates with respect to the first pivot lever 14a.

Further, the projecting portion 14g moves relatively with respect to theelongated insertion hole 14h in accordance with the rotation of thesecond pivot lever 14b with respect to the first pivot lever 14a. Therotation of the second pivot lever 14b with respect to the first pivotlever 14a is regulated at the position at which the projecting portion14g abuts the longitudinal direction end inner surface of the elongatedinsertion hole 14h (position R in FIG. 7). Accordingly, the projectingportion 14g and the elongated insertion hole 14h, which serve as aregulating means, regulate the range of relative movement of the firstpivot lever 14a and the second pivot lever 14b.

In accordance with the present embodiment, even in a state in which thewiper blade 16b is forcibly stopped, because the second pivot lever 14brotates with respect to the first pivot lever 14a, the wiper motor 3 isrotatable and the rotational operation can be continued. Specifically,the rotational operation of the wiper motor 3 can be carried outcontinuously until the locking has been canceled.

Because the rotation portions of the first pivot lever 14a and thesecond pivot lever 14b are connected only at the elastic rubber bush 20,there is no joggling between the first pivot lever 14a and the secondpivot lever 14b, and management of the dimensions of the wiper device 1for a vehicle during manufacturing is facilitated.

During normal wiper wiping operation, the vibration generated by thewiper blade 16b can be decreased by the elastic rubber bush 20 via thepivot shaft 15.

The range of relative rotation between the first pivot lever 14a and thesecond pivot lever 14b can be adjusted by changing the torsionalcharacteristic of the elastic rubber bush 20 or by changing theconfiguration of the elongated through hole 14h. Therefore, there is noneed to make the outer diameter of the elastic rubber bush 20 large withrespect to the abnormal load of the wiper device 1 for a vehicle havinga large wiping angle.

Further, the range of relative rotation of the first pivot lever 14a andthe second pivot lever 14b can be regulated by the projecting portion14g and the elongated insertion hole 14h. Therefore, excessive torsionof the elastic rubber bush 20 can be prevented.

In the present embodiment, the other end of the first pivot lever 14a isstrongly fixed by caulking to the metal, cylindrical portion 14c by thepin 14d. However, as illustrated in FIG. 8, the first pivot lever 14aand the cylindrical portion 14c may be formed integrally by sinteredmetal or the like. In this way, the number of parts can be reduced, andthere is no need for fixing by caulking.

Further, as illustrated in FIG. 9, the positional relationship of theprojecting portion 14g and the elongated through hole 14h, which are theregulating means, can be reversed at the first pivot lever 14a and thesecond pivot lever 14b.

The second pivot lever 19 may be structured in the same way as the firstpivot lever 14 of the present embodiment.

What is claimed is:
 1. A wiper device for a vehicle comprising:a crankarm connected to an output shaft of a motor for rotary motion; a linkrod pivotally connected to said crank arm so as to be freely rotatablewith respect thereto; a pivot lever pivotally connected to said link rodso as to be freely rotatable with respect thereto; and a wiper armconnected to said pivot lever via a pivot shaft for moving a wiper bladeover a windshield, wherein said crank arm is formed by a first leverwhich is connected to the output shaft for rotation therewith, a secondlever which is pivotally connected to said link rod so as to be freelyrotatable with respect thereto, and an elastic bush interposed betweensaid levers and coupled thereto which torsionally deforms elastically,upon excess loading of the wiper blade in accordance with relativerotation between said first lever and said second lever.
 2. A wiperdevice for a vehicle according to claim 1, wherein said elastic bushdamps vibration transmitted from said second lever to said first lever.3. A wiper device for a vehicle according to claim 1, wherein saidelastic bush is adhered and fixed to said first lever and said secondlever.
 4. A wiper device for a vehicle according to claim 3, whereinsaid elastic bush is adhered and fixed to said first lever and saidsecond lever by vulcanization.
 5. A wiper device for a vehicle accordingto claim 1, wherein said elastic bush supports said first lever and saidsecond lever such that said first lever and said second lever can rotaterelatively.
 6. A wiper device for a vehicle according to claim 1,whereinthe output shaft is connected to one end of said first lever, anda cylindrical portion is fixed to another end of said first lever alongan axial direction of the output shaft, and said elastic bush iscylindrical, and an inner peripheral surface of said elastic bush isadhered and fixed to an outer peripheral surface of the cylindricalportion, and a cylindrical hole is formed at one end of said secondlever, and an inner peripheral surface of the cylindrical hole isadhered and fixed to an outer peripheral surface of said elastic bush,and said link rod is connected to another end of said second lever so asto be freely rotatable.
 7. A wiper device for a vehicle according toclaim 1, whereinthe output shaft is connected to one end of said firstlever, and a cylindrical portion is formed integrally with another endof said first lever, and said elastic bush is cylindrical, and an innerperipheral surface of said elastic bush is adhered and fixed to an outerperipheral surface of the cylindrical portion, and said second lever hasa hole formed at one end of said second lever, and an inner peripheralsurface of the hole is adhered and fixed to an outer peripheral surfaceof said elastic bush, and said link rod is connected to another end ofsaid second lever so as to be freely rotatable.
 8. A wiper device for avehicle according to claim 1, whereinthe output shaft is connected toone end of said first lever, and a cylindrical portion is formedintegrally with another end of said first lever, and said elastic bushis cylindrical, and an outer peripheral surface of said elastic bush isadhered and fixed to an inner peripheral surface of the cylindricalportion, and a cylindrical projecting portion, which is fixed to theother end of said first lever along an axial direction of the outputshaft, is formed at one end of said second lever, and an outerperipheral surface of the projecting portion is adhered and fixed to aninner peripheral surface of said elastic bush, and said link rod isconnected to another end of said second lever so as to be freelyrotatable.